1. Field of the Invention
The present invention relates generally to the field of delivering continuous local anesthesia to peripheral nerves. More particularly, it concerns adaptations to a proximal hub of an insulated needle and a method for introducing an “epidural” style catheter through an insulated needle and adjacent to a desired peripheral nerve or nerve plexus in a reliable and safe manner.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
“Regional anesthesia” is a term generally used to describe the practice of rendering select parts (or regions) of the body insensate to painful stimuli. Currently, the most reliable means of achieving regional anesthesia is by application of a local anesthetic to a peripheral nerve or plexus of nerves. By doing so, a particular area is numbed to painful stimuli, which may occur during or after surgery, or from other forms of trauma.
During surgical procedures, it is often desirable to provide regional anesthesia on a continual basis as an infusion, particularly in the postoperative settings. By utilizing regional anesthesia instead of general anesthesia, the post-surgical patient can remain relatively pain-free without systemic side effects, such as nausea or drowsiness, that are generally associated with narcotics and other systemic analgesics.
A standardized medical procedure for providing regional anesthesia as a continuous infusion is the introduction of a peripheral nerve catheter adjacent to the desired nerve or nerve plexus. The term “epidural style” catheter may be alternately used to describe a peripheral nerve catheter. The most common method of localizing the desired nerve or nerve plexus is by applying milliamp levels of current to an insulated needle. The nerve is then located by gradually advancing the insulated needle until the applied current induces visible muscle contraction. In order to achieve muscle contraction, however, the tip of the insulated needle must be within millimeters of the nerve. This allows only a very small margin for error on the part of the anesthesiologist, and obviously to those skilled in the art, any movement of the needle could reduce the effect of the regional anesthetic, damage the nerve, or both.
Conventional catheter systems used for administering local anesthetic (otherwise referred to as “continuous nerve block systems” or “peripheral nerve catheter systems”) are cumbersome and awkward to use in clinical practice. One example of a conventional peripheral nerve catheter system is described in U.S. Pat. No. 5,976,110 and shown in FIG. 1. In general, conventional peripheral nerve catheter system 100 includes a standard epidural catheter threading assist guide 110, which functions to stiffen an epidural catheter 150 so that it can puncture the hemostatic valve (not shown) incorporated within the body of a multipurpose connector 120. The multipurpose connector 120 includes a proximal end 122 adapted for receiving an epidural catheter 150, a distal end 126 adapted for connection to a proximal hub 135 of an insulated needle 130, and a middle aperture 124 adapted for fluid connection to a fluid source 170 via tubing 160. An electrically conductive stimulation wire 140 is coupled for applying a stimulating current to insulated needle 130, which is typically insulated with the exception of the tip of the needle.
However, system 100 suffers from many disadvantages. In particular, most clinicians find it difficult to hold the needle 130, the multipurpose connector 120, and the epidural catheter threading assist guide 110 in one hand 180, while threading the epidural catheter 150 with the other hand 190. To do so, without moving needle 130, provides another level of difficulty. Often, clinicians become frustrated with the multipurpose connector 120 and disconnect it entirely from the proximal hub 135 of insulated needle 130. In such cases, the epidural catheter threading assist guide 110 is inserted into the proximal hub 135 of the insulated needle 130 to assist in threading the epidural catheter 150. The process of removing the multipurpose connector 120 introduces another unnecessary source of potential movement of insulated needle 130. It is therefore desirable to provide a peripheral nerve catheter system that does not require the manipulations required by many of the prior art systems, so that movement of the indwelling needle and catheter is minimized.
Another disadvantage of system 100 is that the multipurpose connector's middle aperture 124 is placed at a 90-degree angle to the shaft of insulated needle 130. This configuration is generally disadvantageous because of the increased likelihood that tubing 160 will kink. In addition, the configuration severely limits the mobility of the system, and in some cases, introduces an additional source of movement for the indwelling needle, due to interference with adjacent anatomical structures. For example, the orthogonal configuration of middle aperture 124 may cause tubing 160 to catch on the patient's right ear during placement of the catheter in the right neck region. It is therefore desirable to provide a system for administering regional anesthesia that does not interfere with anatomical structures. It is a further object of the present invention to provide a system for administering regional anesthesia which, when inserted at a preferred location in a patient's body, does not require the person administering the anesthesia to contact anatomical structures on the patient.
Another disadvantage to system 100 is the likelihood that fluid will reflux out of the system during advancement and/or withdrawal of epidural catheter 150 through the proximal hub 135 of insulated needle 130. For example, if epidural catheter 150 is inserted while fluid is being administered through tubing 160, reflux of the fluid has been known to occur at the point where the epidural catheter penetrates the hemostatic valve within multipurpose connector 120. More specifically, the hemostatic valve may not, in all cases, provide a complete seal around the catheter as it is advanced into (or withdrawn out of) the multipurpose connector. It is therefore desirable to provide a system for administering regional anesthesia that prevents fluid reflux from occurring when epidural catheter 150 is moving (or stationary) within the proximal hub 135.
Multipurpose connector 120 is further described in the above-mentioned patent as an adapter, which must be manually attached to the proximal hub 135 before the epidural catheter can be inserted, and before fluid can be administered, to an indwelling needle. In this manner, fluid reflux may also occur at the interface between multipurpose connector 120 and the proximal hub 135 if multipurpose connector 120 is not properly and securely attached. Therefore, it is further desirable to provide a system for administering regional anesthesia that prevents fluid reflux resulting from the need to manually assemble system components.
FIGS. 2–5 illustrate another peripheral nerve catheter system 200 for administering continuous local anesthetic to peripheral nerves. In the system of FIG. 2, local anesthetic from fluid source 270 is administered through tubing 260 and down the long axis of an insulated needle 230. Similar to system 100, system 200 includes an electrically conductive stimulation wire 240 for applying current to insulated needle 230 for locating a desired nerve or plexus of nerves.
System 200, however, suffers from it's own share of disadvantages. In particular, tubing 260 must be unscrewed from the proximal hub 235 of insulated needle 230 to allow threading of epidural catheter 250. In other words, epidural catheter threading assist guide 210 may only be inserted through the proximal hub 235 of insulated needle 230 after tubing 260 is removed. FIG. 3 is a view of the catheter system of FIG. 2 illustrating the removal of tubing 260 in preparation for threading epidural catheter 250 through the proximal hub 235 of insulated needle 230. FIG. 4 is a view of insulated needle 230 with epidural threading assist guide 210 inserted into the proximal hub 235 of the insulated needle.
FIG. 5 illustrates the process of threading epidural catheter 250 through epidural catheter threading assist guide 210 and into insulated needle 230. As before, movement associated with the removal of tubing 260 may cause the insulated needle to become misplaced. In some cases, misplacement of the insulated needle may reduce the effectiveness of the local anesthetic or may increase the time needed for correctly positioning the epidural catheter. Misplacement of the needle may even cause nerve damage by directly contacting the nerve. Thus, a major disadvantage of system 200 results from the fact that tubing 260 must be disconnected from proximal hub 235 in order to connect catheter 250. In addition to tubing disconnections, system 200 requires manual insertion of thread guides (such as, e.g., catheter threading assist guide 210) for placing the epidural catheter within the patient. It is therefore desirable to provide a system for administering regional anesthesia without requiring disconnection of tubing (such as, e.g., tubing 260) or manual insertion of thread guides.
Regardless of whether system 100 or system 200 is used, there is a danger that the epidural catheter may kink during insertion through a hemostatic valve or a proximal hub. At best, a kinked catheter may be more difficult to thread through the insulated needle. In some situations, however, kinking of the catheter may occlude the orifice of the catheter (making it nearly impossible to administer anesthesia) or may cause a portion of the catheter to shear off into the patient (due to contact with a beveled edge of the needle tip). As such, anesthesiologists often find it safer to remove portions of the catheter system (e.g. multipurpose connector 120 of FIG. 1) to make it easier to thread the epidural catheter without the danger of kinking the catheter. It is therefore desirable to provide a system with features that reduce the dangers associated with threading the epidural catheter through the needle.
It is therefore desirable to provide a peripheral nerve catheter system with features that reduce or eliminate opportunities for an indwelling needle or catheter to move once the needle is near a nerve or nerve plexus.